<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    
    <title>监视属性-天气案例</title>
    <script type="text/javascript" src="../js/vue.js"></script>
</head>
<body>
    <div id="root">
        <h2>今天天气很{{info}}</h2>
        <!--@xxx 事件可以写一些简单的语句-->
        <button @click="isHot = !isHot;">切换天气状态</button>
        <button @click="changeWeather">切换天气状态</button>
    </div>
</body>
<script type="text/javascript" >
 const vm = new Vue({
   el:'#root', 
   data: { 
    isHot:true,
   },
   computed:{
    info(){
        return this.isHot ? '炎热' : '凉爽'
    }
   },
   methods: {
    changeWeather(){
        this.isHot = !this.isHot;
    }
   },
//    watch:{
//     isHot:{
//         immediate:true, //初始化时让handler调用一下
//         handler(newValue,oldValue){
//             console.log('isHot被修改了',newValue,oldValue);
//         }
//     }
//    }

 });
 vm.$watch('isHot',{
    immediate:true, //初始化时让handler调用一下
        handler(newValue,oldValue){
             console.log('isHot被修改了',newValue,oldValue);
         }
 });
 vm.$watch('info',{
    immediate:true, //初始化时让handler调用一下
        handler(newValue,oldValue){
             console.log('info被修改了',newValue,oldValue);
         }
 })
</script>
</html>